Chronic kidney disease (CKD) is a disease that progresses when a finding indicative of kidney damage or a state where deterioration of kidney function chronically continues remains untreated. As it progresses, the disease results in end-stage renal failure, and survival without artificial dialysis or kidney transplantation becomes difficult.
End-stage renal failure is increasing on a global scale. To deal with this disease, early treatment and early detection, specifically detection when the disease is so-called “hidden chronic kidney disease,” are said to be important.
It is said that there are currently about 13,300,000 CKD patients in Japan. This indicates that about 1 in 8 adults is a CKD patient.
The most commonly occurring primary disease among dialysis patients is diabetic nephropathy, which is one of the three major diabetic complications. Since diabetic nephropathy is one of the CKDs, patients with diabetes are likely to get CKD. According to the National Health and Nutrition Examination Survey in 2006 (Ministry of Health, Labor and Welfare), the number of diabetic patients is estimated to be 8,200,000, and 18,700,000 including potential diabetic patients. Since it is assumed that 30 percent of these patients will develop renal failure, the number of CKD patients will continue to increase in the future. The annual medical expenses for dialysis treatment in Japan are, for example, approximately 5,400,000 yen per person, and 1.5 trillion yen as a whole. Since the number of dialysis patients is increasing, the medical expenses required for dialysis treatment are also increasing. Therefore, measures to curtail these medical expenses are urgently needed. For this reason, early detection of kidney damage, early treatment to prevent symptom aggravation, and, in the end, reduction of the number of patients introduced to dialysis as much as possible are considered globally important.
CKD is staged according to the glomerular filtration rate (GFR), which is an evaluation index of kidney function. Namely, CKD is classified into five stages, according to GFR (NPL 1).
However, the thus-performed determination of CKD staging is based on the serum creatinine concentration. Since the serum creatinine concentration is strongly affected by muscle mass, there is a problem such that performing an accurate determination excluding such an influence is difficult. Further, since an increase in the serum creatinine concentration is not observed until the estimated GFR (eGFR) becomes 50% or less, minor kidney damage is difficult to find. Despite such circumstances, appropriate determination methods in place of the aforementioned method have not been developed.